Crystals have been used as resonators in resonation or oscillation circuitry for about as long as radio devices have been around. So the well-known drawbacks of using crystals in oscillator and/or filtering circuits are that they are relatively expensive with respect to the manufacturing costs of mass-produced integrated circuits. Furthermore, crystals cannot be directly mounted to an integrated circuit. Crystals must be sealed in a special container that is separate from an integrated circuit. These special containers are used to stop contamination of the crystal. Such contamination by dirt particles would vary the oscillation frequency of the crystal. In addition crystals have reliability problems wherein crystals oscillate at substantially different base frequencies depending on their surrounding temperature.
Research has led to a family of new devices that are possible viable replacements for the crystal oscillator of yesteryear. Such new devices are called microelectronic machines (MEMs). To date, single frequency MEMs are thought to be capable of providing the basis for a high Q oscillator that equals or exceeds the capability of crystal oscillators. A high Q factor for an oscillator describes how under damped and oscillator or resonator is, or equivalently, characterizes a resonator's bandwidth relative to its center frequency. The higher the Q, the lower the rate of energy loss relative to the stored energy of the resonator. For example, a single frequency MEM oscillator can be easily incorporated into a silicon device; thus, additional space for an external crystal is no longer required. Furthermore, single frequency MEMs have been designed to provide cost efficient reliability performance over temperature ranges that exceeds various crystal based oscillators and radio frequency (RF) filter circuitry.